Preparation of 4-substituted but-3-ene-1-carboxylic acids and their esters

ABSTRACT

4-Substituted but-3-ene-1-carboxylic acids and their esters R 1  R 2  C═CH--CH 2  --CO--O--R 3  (I, where R 1  is an organic radical, R 2  is H or R 1 , or R 1  and R 2  together form a 5-membered to 20-membered ring, and R 3  is H or lower alkyl) are prepared by carbonylation of R 1  R 2  C(OH)--CH═CH 2  (II) in the presence of an alcohol R 3&#39;  --OH (III, where R 3&#39;   is lower alkyl) or, for the preparation of the acids I alone, in the absence of an alcohol III, at from 50° to 150° C. and under from 200 to 700 bar, using a complex of a palladium halide and a tertiary organic phosphine.

The present invention relates to a novel process for the preparation of4-substituted but-3-ene-1-carboxylic acids or their esters of thegeneral formula I ##STR1## where R¹ is an organic radical, R² ishydrogen or an organic radical, and R¹ and R² may furthermore be bondedto one another to form a 5-membered to 20-membered ring and should beinert under the reaction conditions described below, and R³ is hydrogenor lower alkyl.

Tsuji et al., in J. Am. Chem. Soc. 86 (1964), 4350-4353, disclose thatethyl pent-3-ene-1-carboxylate (I, where R¹ is Me, R² is H and R³ is Et)can be prepared by carbonylation of but-1-en-3-ol with carbon monoxideand ethanol in the presence of palladium chloride as a carbonylationcatalyst. However, the yield of only 39% achieved in this procedure isunsatisfactory for industrial purposes.

Furthermore, Bittler et al., in Angew. Chemie, 80 (1968), 352-359,disclose that allyl alcohol and methanol can be carbonylated using apalladium chloride/triphenylphosphine complex to give methylbut-3-enecarboxylate in 65% yield. According to the authors (cf. loccit, page 355), the carbonylation of the allyl alcohol takes place withretention of the double bond, so that the 4-substitutedbut-3-enecarboxylates have to be prepared using, as starting materials,the allyl alcohols ##STR2## which are difficult to obtain.

It is an object of the present invention to make the compounds I morereadily accessible, these compounds generally being important fororganic syntheses, and some of them being directly useful as fragrancematerials.

We have found, unexpectedly in view of the work by Bittler et al., thatthis object is achieved by a process for the preparation of thecompounds (I) defined at the outset, by carbonylation of a derivative ofallyl alcohol with the aid of a palladium halide, wherein an allylalcohol II ##STR3## is carbonylated with carbon monoxide at 50°-150° C.and under 200-700 bar,

(a) together with an alcohol III

    R.sup.3' --OH                                              (III)

where R^(3') is lower alkyl, if a predominant amount of an ester I is tobe prepared, or

(b) without a further reactant where an acid I is to be prepared, in thepresence of an effective amount of a complex of a palladium halide and atertiary phosphine (IV).

The starting compounds II are obtainable in a simple manner from thecorresponding carbonyl compounds R¹ --CO--R² and vinyl magnesiumhalides. II can also be prepared from the carbonyl compounds andacetylides, such as sodium acetylide, with subsequent partialhydrogenation of the ethynyl group to the vinyl group.

On the basis of the very extensive investigations carried out to date,the nature of the compounds II, ie. the type of organic radicals R¹ andR², is in principle unimportant with regard to the novel process,provided that these radicals do not contain any substituents or groupswhich are reactive under the carbonylation conditions. Examples of suchreactive radicals are alkenyl groups having terminal double bonds; if,on the other hand, the double bond is an internal one, it is as a rulevirtually never attacked under the reaction conditions.

Examples of suitable radicals R¹ and R² are aliphatic radicals of 1 to30 carbon atoms, cycloaliphatic radicals having 3 to 12 ring members,aromatic radicals possessing from 1 to 3 isocyclic or heterocyclicaromatic rings, mixed radicals containing aliphatic and/orcycloaliphatic and/or aromatic groups in any sequence, and cyclicradicals which have from 3 to 20 ring members, are formed by R¹ and R²together and can in turn be substituted by the above radicals.

All of these radicals can furthermore contain substituents such ashalogen, eg. fluorine or chlorine, hydroxyl (which in general isvirtually never attacked during the carbonylation according to theinvention), substituted amino, cyano, nitro, alkoxy, acyl, acyloxy,carbalkoxy, thiol, mercaptan, carboxamide or alkylsulfonyl. Particularlyimportant alcohols II are those whose molecule contains one or moreisoprene skeletons; the compounds I derived from these are often typicalfragrance materials.

Suitable alcohols III are mainly lower alcohols, such as methanol andethanol, since the carbonylation proceeds most rapidly with these.Higher alcohols of not more than about 6 carbon atoms can in principlealso be used, although it is frequently more advantageous to introducethese into the molecule by transesterification of the methyl or ethylesters I.

In general, it is preferable to use a molar excess of the alcohol IIIover the alcohol II. Usually, the molar ratio of III to II is from 2:1to 6:1. If III is used as a solvent, this ratio may also be higher.

If the procedure is carried out in the absence of a further reactant,ie. without an alcohol III, the acids I are obtained. Predominantamounts of acid are also generally obtained when a tertiary alcohol III,eg. tert.-butanol, is used.

The carbonylation catalysts are complexes of a palladium halide, eg. thebromide or in particular the chloride, and a tertiary organic phosphine(IV). Since formation of these complexes takes place directly under thereaction conditions, the said complexes are advantageously employed inthe form of their components; however, it is of course also possible tostart from the preprepared complexes, eg. Pd(PPh₃)₂ Cl₂ (Ph=phenyl).

The tertiary phosphines IV are of the general formula IV ##STR4## whereR⁴, R⁵ and R⁶ are each an organic radical.

In particular, R⁴, R⁵ and R⁶ can each be alkyl of 4 to 18 carbon atoms,C₁ -C₄ -alkylphenyl or, especially, phenyl. Two of these radicals mayfurthermore be bonded to one another to form a 5-membered to 8-memberedring, and it is of course also possible to use compounds possessing 2 ormore tertiary phosphine groups, eg. 1,2-bis-(diphenylphosphino)-ethane.

The type of phosphines is in principle unimportant, so that it is ingeneral preferable to use the cheapest member of this class ofsubstances, ie. triphenylphosphine.

It is also advantageous to carry out the reaction in the presence offree phosphine, ie. phosphine which is not bonded in a complex. Thepreferred molar ratio of phosphine to Pd is from 3:1 to 10:1.

It is not possible to state a particular value for the effective amountof the catalyst because the reaction takes place in principle withinfinitely small amounts of Pd, but is of course then very slow, andbecause large amounts have no adverse effect. Hence, the amount of Pddepends on the reactivity of the alcohol II and on the reaction timedesired. In general, the amount of Pd is from 0.1 to 5 g per mole of II.

According to the general principles of process engineering, the reactiontakes place most readily and most rapidly in the substantiallyhomogeneous liquid phase. In general, homogeneity results automaticallyunder the reaction conditions owing to the presence of the alcohol III,so that an additional solvent need not be used. If, however, the alcoholII is sparingly soluble, it is advisable to use a solvent, such astoluene, diethyl ether or tetrahydrofuran.

The pressure, which for the most part corresponds to the CO partialpressure, is in general from 100 to 650, in particular from 300 to 600,bar, and the recommended temperature is from 50° to 150° C., preferablyfrom 90° to 110° C. Under these conditions, and using the recommendedamounts of catalyst, the reaction times are about 1-24 hours.

The novel process can be carried out continuously or batchwise, and themethod used is identical to the conventional carbonylation technique, sothat more detailed description of this can be dispensed with. The sameapplies to the working up of the reaction mixtures. Owing to thesensitivity of the phosphines to oxidation, it is advisable to carry outthe procedure in the absence of atmospheric oxygen.

When the alcohol III is also used, the products obtained are mainly theesters I, the free acids 1 also resulting; tertiary alcohols IIIgenerally give larger amounts of the acid. The amount of by-products islow in every case, although it was expected that the alcohols II wouldbe dehydrated under the reaction conditions. The compounds I can beformed in the cis or trans form, predominant amounts of the trans isomerusually being obtained.

EXAMPLES

Various alcohols II were reacted with various alcohols III, in each casein the absence of atmospheric oxygen, at 100° C., in the presence ofpalladium chloride and triphenylphosphine (Pph₃), to give the acids oresters I.

Details of the other reaction conditions and of the results of theexperiments are shown in the Table below. About 98% of the statedpressure is due to the CO partial pressure. Each of the reactions wasterminated when scarcely any further CO was consumed.

The products were identified by means of gas chromatographic, H--NMR, ¹³C--NMR, mass spectroscopic and IR analysis. The yields were determinedgravimetrically; where separation into the acid and the ester presenteddifficulties, only the sum of the yields was determined. Boiling pointsand melting points are stated wherever they were obtained directly fromthe experiments.

    __________________________________________________________________________                                 Pres-   Yields acid/ester I                      Ex- Alcohol II   Alcohol III                                                                          PdCl.sub.2 [g]                                                                     sure                                                                             Duration                                                                           Total yield, trans/cis ratio q           ample                                                                             [g]          [g]    PPh.sub.3 [g]                                                                      [bar]                                                                            [h]  Characteristics                          __________________________________________________________________________     1  Pent-1-en-3-ol                                                                             MeOH   1.0  600                                                                              17   14%                                                                              hex-3-enoic acid                          100          50     3.0          78%                                                                              methyl hex-3-enoate, bp.                                                      100-101° C./                                                        92%                                                                              q = 85:15 231 mbar                     2  Hex-1-en-3-ol                                                                              EtOH   1.0  600                                                                               8   15%                                                                              hept-3-enoic acid                         100          50     3.0          54%                                                                              ethyl hept-3-enoate, bp.                                                      89° C./45 mbar                                                      69%                                                                              q = 85:15                                                                     scent, acid: greenish, fruity,                                                some-                                                                         what pungent                                                                  ester: sweetish, floral,                                                      somewhat                                                                      tonka-like                             3  Hept-1-en-3-ol                                                                             EtOH   5.0  300                                                                              15   18%                                                                              oct-3-enoic acid                          920          500    1.5          69%                                                                              ethyl oct-3-enoate, bp.                                                       112-114° C./                                                        87%                                                                              q = 80:20 54 mbar                                                             scent, acid and ester: greenish,                                              slightly fatty                         4  Oct-1-en-3-ol                                                                              n-propanol                                                                           5.0  300                                                                               8   15%                                                                              non-3-enoic acid                          730          500    15.0         64%                                                                              n-propyl non-3-enoate, bp.                                                    70-72° C./                                                          79%                                                                              q = 82:18 4 mbar                                                              scent, ester: green, slightly                                                 herbaceous, fungal                     5  3-Methylbut-1-en-3-ol                                                                      MeOH   2.5  300                                                                               8    9%                                                                              4-methylpent-3-enoic acid, bp.                                                122° C./                           1,000        500    7.5          47%                                                                              48 mbar                                                                    56%                                                                              methyl 4-methylpent-3-enoate,                                                 bp. 110° C./150 mbar            6  3,7-Dimethyloct-1-en-3-ol                                                                  i-propanol                                                                           2.5  300                                                                               8   23%                                                                              4,8-dimethylnon-3-enoic acid,             1,000        500    7.5          57%                                                                              bp. 165° C./45 mbar                                                 80%                                                                              isopropyl 4,8-dimethylnon-3-enoate                                            ,                                                                             bp. 145° C./37 mbar                                                    q =  87:13                             7  3,7-Dimethyloct-1-en-3-ol                                                                  n-propanol                                                                           5    300                                                                               8   13%                                                                              4,8-Dimethylnon-3-enoic acid              1,000        500    15           68%                                                                              n-propyl 4,8-dimethylnon-3-enoate,                                            3                                                                          81%                                                                              bp. 147° C./34 mbar                                                    cis-ester: sweetish, balsamic,                                                fruity                                                                        trans-ester: floral, somewhat                                                 fatty                                  8  3,7-Dimethyloct-1-en-3-ol                                                                  n-butanol                                                                            5    300                                                                              15   17%                                                                              4,8-dimethylnon-3-enoic acid              1,000        5,000  15           63%                                                                              n-butyl 4,8-dimethylnon-3-enoate,                                             .                                                                          80%                                                                              bp. 160° C./37 mbar                                                    q = 66:34                              9  3,7-Dimethylocta-1,6-                                                                      EtOH   5    250                                                                              14   22%                                                                              4,8-dimethylnona-3,7-dienoic                                                  acid                                      dien-3-ol    500    15           61%                                                                              ethyl 4,8-dimethylnona-3,7-dienoat                                            e                                         1,000                            83%                                                                              bp. 82-84° C./4 mbar                                                   q = 68:32                                                                     cis-ester: fruity, greenish                                                   trans-ester: pleasantly fruity,                                               musk-like                             10  3,7-Dimethylocta-1,6-                                                                      EtOH   2.5  300                                                                              10   34%                                                                              4,8-dimethylnona-3,7-dienoic                                                  acid                                      dien-3-ol    500    7.5          56%                                                                              ethyl 4,8-dimethylnona-3,7-dienoat                                            e                                         1,000                            90%                                                                              bp. 82° C./4 mbar              11  3,7,11-Trimethyldodec-                                                                     EtOH   2.5  300                                                                               6    3%                                                                              4,8,12-trimethyltridec-3-enoic                                                acid                                      1-en-3-ol    205    7.5          90%                                                                              ethyl 4,8,12-trimethyltridec-3-eno                                            ate                                       410                              93%                                                                              bp. 125-130° C./4 mbar                                                 q = 80:20                             12  3,7,11-Trimethyldodeca-                                                                    MeOH   2.5  300                                                                               6   11%                                                                              4,8,12-trimethyltrideca-3,7-dienoi                                            c                                         1,6-dien-3-ol                                                                              500    7.5          63%                                                                              acid                                      (dihydronerolidol)               74%                                                                              methyl 4,8,12-trimethyltrideca-3,7                                            -                                         1,125                               dienoate, bp. 125-129°                                                 C./4 mbar                             13  3,7,11-Trimethyl-dodeca-                                                                   EtOH   5    300                                                                               8    6%                                                                              4,8,12-trimethyltrideca-3,7-dienoi                                            c                                         1,6-dien-3-ol                                                                              500    15           81%                                                                              acid                                      (dihydronerolidol)               87%                                                                              ethyl 4,8,12-trimethyltrideca-3,7-        1,000                               dienoate                              14  3,7,11-Trimethyl-dodeca-                                                                   MeOH   2.5  300                                                                              10    7%                                                                              4,8,12-trimethyltrideca-3,7,11-           1,6,10-trien-3-ol                                                                          500    7.5          79%                                                                              trienoic acid                             (nerolidol)                      86%                                                                              methyl 4,8,12-trimethyltrideca-           1,000                               3,7,11-trienoate,                                                             bp. 129-130° C./4 mbar         15  3,7,11-Trimethyl-dodeca-                                                                   EtOH   2.5  300                                                                              14    7%                                                                              4,8,12-trimethyltrideca-3,7,11-           1,6,10-trien-3-ol                                                                          500    7.5          79%                                                                              trienoic acid                             (nerolidol)                      86%                                                                              ethyl 4,8,12-trimethyltrideca-3,7,                                            11-                                       1,000                               trienoate, bp. 126-130°                                                C./4 mbar                             16  3,7,11-Trimethyl-dodeca-                                                                   EtOH   1.25 300                                                                              17    9%                                                                              4,8,12-trimethyltrideca-3,7,11-           1,6,10-trien-3-ol                                                                          500    3.75         69%                                                                              trienoic acid                             (nerolidol)                      77%                                                                              ethyl 4,8,12-trimethyltrideca-3,7,                                            11-                                       1,000                               trienoate, bp. 127-152°                                                C./4 mbar                             17  3,7,11,15-Tetramethyl-                                                                     EtOH   2.5  300                                                                              19    4%                                                                              4,8,12,16-tetramethylheptadec-3-          hexadec-1-en-3-ol                                                                          500    7.5          90%                                                                              enoic acid                                (isophytol)                      94%                                                                              ethyl 4,8,12,16-tetramethylheptade                                            c-                                        1,000                               3-enoate, bp. 162-167°                                                 C./4 mbar                                                                     q = 3:1                               18  5-(2,6,6-Trimethylcyclo-                                                                   EtOH   3.5  300                                                                               4    8%                                                                              6-(2,6,6-trimethylcyclohex-1-yl)-4                                            -                                         hex-1-en-1-yl)-3-methyl-                                                                   300    10.0            methylhex-3-enoic acid                    pent-1-en-3-ol                   76%                                                                              ethyl 6-(2,6,6-trimethylcyclohex-1                                            -                                         600                              84%                                                                              yl)-4-methylhex-3-enoate,                                                     bp. 148-157° C./5 mbar                                                 q = 82:18                                                                     cis-ester: sweet fruity (apple,                                               strawberry)                           19  5-(2,6,6-Trimethylcyclo-                                                                   EtOH   1.0  600                                                                              10   *  6-(2,6,6-trimethylcyclohex-1-enyl)                                            -                                         hex-1-en-1-yl)-3-methyl-                                                                   50     3.0             4-methylhexa-3,5-dienoic acid             penta-1,4-dien-3-ol                 ethyl 6-(2,6,6-trimethylcyclohex-1                                            -                                         (vinylionol)                        enyl)-4-methylhexa-3,5-dienoate,          100                                 bp. 159-162° C.                                                     25%                                                                              mixture: fruity, damsony                                                      apricot                               20  3-Ethylpent-1-en-3-ol                                                                      EtOH   1.0  600                                                                              22   11%                                                                              4-ethylpent-3-enoic acid                  120          60     3.0          54%                                                                              ethyl 4-ethylpent-3-enoate,                                                   bp. 106-107° C./52 mbar                                             65%                                                                              ester: pungent, greenish, fruity      21  4-Vinylheptan-4-ol                                                                         EtOH   1.0  600                                                                              17    6%                                                                              4-n-propylhept-3-enoic acid               100          50     3.0          56%                                                                              ethyl 4-n-propylhept-3-enoate,                                                bp. 53-55° C./4 mbar                                                62%                                                                              ester: fruity, green, rubbery         22  1-Vinylcyclododecan-1-ol                                                                   EtOH   1.0  600                                                                              23    8%                                                                              3-(cyclododecylidene)-propionic                                               acid                                      100          50     3.0          61%                                                                              ethyl 3-(cyclododecylidene)-propio                                            n-                                                                            ate, bp. 144-146° C./4                                                 mbar                                                                       69%                                                                              ester: fatty, tart, slightly                                                  sweetish,                                                                     balsamic                              23  2-Methyl-1-vinyl-cyclo-                                                                    EtOH   1.0  600                                                                              17    5%                                                                              3-(2-methylcyclohexylidene)-              hexan-1-ol   46.7   3.0             propionic acid                            93.5                             51%                                                                              ethyl 3-(2-methylcyclohexylidene)-                                         56%                                                                              propionate, bp. 116-122°                                               C./28 mbar                            24  3-Methyl-1-vinyl-cyclo-                                                                    EtOH   1.0  600                                                                              34    5%                                                                              3-(3-methylcyclohexylidene)-              hexan-1-ol   46     3.0             propionic acid                            92                               73%                                                                              ethyl 3-(3-methylcyclohexylidene)-                                         78%                                                                              propionate, bp. 105-110°                                               C./16 mbar                                                                    ester: fruity, sweetish, fatty                                                alcohol-like                          25  1-Vinyl-cyclohexan-1-ol                                                                    EtOH   2.5  300                                                                              17   12%                                                                              3-(cyclohexylidene)-propionic                                                 acid                                      876          500    7.5          58%                                                                              ethyl 3-(cyclohexylidene)-propiona                                            te                                                                         70%                                                                              bp. 130° C./30 mbar                                                    ester: fruity, strawberry-like,                                               tart                                  26  3,3-Dimethyl-1-vinyl-                                                                      EtOH   1.0  600                                                                               7    3%                                                                              3-(3,3-dimethylcyclohexylidene)-          cyclohexan-1-ol                                                                            50     3.0             propionic acid,                           90                               76%                                                                              ethyl 3-(3,3-dimethylcyclohexylide                                            ne)-                                                                          propionate, bp. 138-140°                                               C./40 mbar                                                                 79%                                                                              q = 50:50                                                                     ester: woody, fruity, greenish        27  Mixture of 2,2,4- and                                                                      EtOH   1.0  600                                                                              16    4%                                                                              3-(2,2,4/2,4,4-trimethylcyclopenty                                            li-                                       2,4,4-trimethyl-1-vinyl-                                                                   50     3.0             dene)-propionic acid                      cyclopentan-1-ol                 58%                                                                              ethyl 3-(2,2,4/2,4,4-trimethylcycl                                            o-                                        100                                 pentylidene)-propionate,                                                      bp. 62-63° C./4 mbar                                                62%                                                                              ester: green, earthy, fungal,                                                 woody                                 28  1-Vinyl-1-hydroxy-                                                                         EtOH   1.0  600                                                                              13    5%                                                                              2,3-benzocyclohexylid-1-enepropion                                            ic                                        1,2,3,4-tetrahydro-                                                                        100    3.0             acid                                      naphthalene                      60%                                                                              ethyl 2,3-benzocyclohexylid-1-ene-        100                                 propionate, bp. 110° C./4                                              mbar                                                                       65%                                                                              q = 70:30                             29  9-Vinyl-9-hydroxy-                                                                         EtOH   1.0  600                                                                              10   <1%                                                                              3-(fluorenylid-9-ene)-propionic                                               acid                                      fluorene     50     3.0           83%                                                                             ethyl 3-(fluorenylid-9-ene)-propio                                            n-                                        85                                83%                                                                             ate, bp. 60-65° C.             30  3,3-Diphenylprop-1-en-3-                                                                   EtOH   1.0  600                                                                              10    8%                                                                              4,4-diphenylbut-3-enoic acid              ol           50     3.0          72%                                                                              ethyl 4,4-diphenylbut-3-enoate,           73                               80%                                                                              bp. 168° C./4 mbar             31  3-Phenylbut-1-en-3-ol                                                                      EtOH   1.0  600                                                                               8    5%                                                                              4-phenyl-but-3-enoic acid                 70           50     3.0          40%                                                                              ethyl 4-phenyl-but-3-enoate bp.                                               159° C./40 mbar                                                     30%                                                                              2-methyl-2-phenylbutyrolactone,                                            75%                                                                              bp. 165-167° C./40 mbar        32  3-(3,3-Dimethylcyclo-hex-                                                                  EtOH   1.0  600                                                                               5    8%                                                                              4-(3,3-dimethylcyclohex-1-yl)-pent                                            -                                         1-yl)-but-1-ene                                                                            50     3.0             3-enoic acid                              100                              65%                                                                              ethyl 4-(3,3-dimethylcyclohex-1-yl                                            )-                                                                            pent-3-enoate,                                                                bp. 80-82° C./4 mbar                                                73%                                                                              q = 1:1                               33  3-Cyclopropylbut-1-en-3-                                                                   EtOH   1.0  600                                                                              15    4%                                                                              4-cyclopropylbut-3-enoic acid             ol           50     3.0          38%                                                                              ethyl 4-cyclopropylbut-3-enoate,          100                              42%                                                                              bp. 113-115° C./44 mbar        34  3-Methoxybut-1-en-3-ol                                                                     EtOH   1.0  530                                                                              12    4%                                                                              4-methoxypent-3-enoic acid                80           50     3.0          38%                                                                              ethyl 4-methoxypent-3-enoate,                                                 bp. 117-125° C./74 mbar                                             42%                                                                              q = 80:20                             35  3-Methyl-4-phenyl-but-1-                                                                   EtOH   1    680                                                                              20   12%                                                                              4-methyl-5-phenyl-but-3-enoic                                                 acid                                      en-3-ol      50     3            68%                                                                              ethyl 4-methyl-5-phenyl-but-3-enoa                                            te,                                       101                                 bp. 98-99° C./4 mbar                                                80%                                                                              q = 65:35                                                                     ester: green, pelargonium leaves      36  1-Vinyl-cycloheptan-1-ol                                                                   EtOH   1    600                                                                              13   11%                                                                              3-cycloheptylidene-propionic                                                  acid                                      105          45     3            58%                                                                              ethyl 3-cycloheptylidene-propionat                                            e                                                                          69%                                                                              bp. 132° C./24 mbar            37  3-(4-Methoxyphenyl)-but-                                                                   EtOH   1    300                                                                              16    2%                                                                              4-(4-methoxyphenyl)-pent-3-enoic                                              acid                                      1-en-3-ol    50     3            40%                                                                              ethyl 4-(4-methoxyphenyl)-pent-3-         100                                 enoate, bp. 157-159° C./40                                             mbar                                                                       33%                                                                              5-(4-methoxyphenylmethyl)-butyrola                                            c-                                                                         75%                                                                              tone, bp. 165-167° C./40                                               mbar                                  38  4-tert.-Butoxy-hex-1-                                                                      EtOH   0.5  300                                                                              11   11%                                                                              5-tert.-butoxy-hept-3-enoic acid          en-3-ol      50     1.5          52%                                                                              ethyl 5-tert.-butoxy-hept-3-enoate                                            ,                                         58                               63%                                                                              bp. 85-86° C./4 mbar           39  3-(2-Methoxyphenyl)-but-                                                                   EtOH   0.5  300                                                                              26    8%                                                                              4-(2-methoxyphenyl)-pent-3-enoic                                              acid                                      1-en-3-ol    50     1.5          72%                                                                              ethyl 4-(2-methoxyphenyl)-pent-3-         37                               80%                                                                              enoate, bp. 122-128° C./4                                              mbar                                  40  2-Benzyl-1-vinyl-cyclo-                                                                    EtOH   1    600                                                                              26    4%                                                                              3-(2-benzylcyclohexylidene)-propio                                            nic                                       hexan-1-ol   37     3               acid                                      37                               79%                                                                              ethyl 3-(2-benzylcyclohexylidene)-                                         83%                                                                              propionate, bp. 163-182°                                               C./4 mbar                             41  3-(Tetrahydropyran-3-yl)-                                                                  EtOH   1    650                                                                              13   11%                                                                              4-(tetrahydropyran-3-yl)-but-3-           prop-1-en-3-ol                                                                             50     3               enoic acid                                100                              66%                                                                              ethyl 4-(tetrahydropyran-3-yl)-but                                            -                                                                             3-enoate, bp. 72-74° C./4                                              mbar                                                                       77%                                                                              q = 90:10                             42  Bis-(4-chlorophenyl)-                                                                      EtOH   1    650                                                                               7    8%                                                                              4,4-di-(4-chlorophenyl)-but-3-enoi                                            c                                         vinylcarbinol                                                                              50     3               acid                                      100                              63%                                                                              ethyl 4,4-di-(4-chlorophenyl)-but-                                            3-                                                                         71%                                                                              enoate, bp. 208-212° C./4                                              mbar                                  43  Bis-(4-fluorophenyl)-                                                                      EtOH   1    650                                                                               6    5%                                                                              4,4-di-(4-fluorophenyl)-but-3-            vinylcarbinol                                                                              30     3               enoic acid                                115                              68%                                                                              ethyl 4,4-di-(4-fluorophenyl)-but-                                         73%                                                                              3-enoate, bp. 148-153°                                                 C./4 mbar                             44  1-Vinyl-2,3-6,7-dibenzo-                                                                   EtOH   1    650                                                                               8    4%                                                                              3-(2,3-6,7-dibenzo-cyclohept-4-en-                                            1-                                        cyclohept-4-en-1-ol                                                                        50     3               ylidene)-propionic acid                   105                              69%                                                                              ethyl 3-(2,3-6,7-dibenzo-cyclohept                                            -                                                                             4-en-1-ylidene)-propionate,                                                73%                                                                              bp. 168-170° C./4 mbar         45  1-Vinyl-2,3-6,7-dibenzo-                                                                   EtOH   1    650                                                                               6    3%                                                                              3-(2,3-6,7-dibenzocyclohept-1-yli-        cycloheptan-1-ol                                                                           50     3               dene-propionic acid                       100                              69%                                                                              ethyl 3-(2,3-6,7-dibenzocyclohept-                                            1-                                                                         72%                                                                              ylidene-propionate, bp.                                                       182-185° C./4 mbar             46  3-(2-Methoxyphenyl)-prop-                                                                  EtOH   1    650                                                                              12    8%                                                                              4-(2-methoxyphenyl)-but-3-enoic                                               acid                                      1-en-3-ol    50     3            59%                                                                              ethyl 4-(2-methoxyphenyl)-but-3-          103                              67%                                                                              enoate, bp. 146-153° C./7                                              mbar                                  47  3,7-Dimethyl-octa-1,6-                                                                     tert.-ButOH                                                                          2.5  300                                                                               9   66%                                                                              4,8-dimethyl-nona-3,7-dienoic                                                 acid                                      dien-3-ol    500    7.5          20%                                                                              tert.-butyl 4,8-dimethyl-nona-3,7-        1,000                            86%                                                                              dienoate, bp. 97-98° C./6                                              mbar                                  48  3,7-Dimethyl-oct-1-en-3-                                                                   tert.-ButOH                                                                          2.5  300                                                                              13   64%                                                                              4,8-dimethyl-non-3-enoic acid,            ol           500    7.5          18%                                                                              tert.-butyl 4,8-dimethyl-non-3-eno                                            ate,                                      1,000                            82%                                                                              bp. 88° C./4 mbar              49  3-Methyl-but-1-en-3-ol                                                                     tert.-ButOH                                                                          2.5  300                                                                              22   71%                                                                              4-methyl-but-3-enoic acid                 1,000        500    7.5          13%                                                                              tert.-butyl 4-methyl-but-3-enoate,                                         84%                                                                              bp. 87° C./48 mbar             50  3-Methyl-but-1-en-3-ol                                                                     tert.-ButOH                                                                          2.5  300                                                                              41   58%                                                                              4-methyl-but-3-enoic acid                 1,000        500    7.5**        15%                                                                              tert.-butyl 4-methyl-but-3-enoate,                                         73%                                                                              bp. 87° C./48 mbar             51  Oct-1-en-3-ol                                                                              tert.-ButOH                                                                          2.5  300                                                                              32   63%                                                                              oct-3-enoic acid                          1,000        500    7.5          12%                                                                              tert.-butyl oct-3-enoate,                                                  75%                                                                              bp. 72° C./6 mbar              52  3,7,11-Trimethyl-dodeca-                                                                   tert.-ButOH                                                                          2.5  300                                                                              32   74%                                                                              4,8,12-trimethyl-trideca-3,7,11-          1,6,10-trien-3-ol                                                                          500    7.5             trienoic acid                             (nerolidol)                       3%                                                                              tert.-butyl 4,8,12-trimethyl-tride                                            ca-                                       1,000                               3,7,11-trienoate                                                           77%                                                                              isomer mixture                        53  3,7,11-Trimethyl-dodeca-                                                                   tert.-ButOH                                                                          2.5  300                                                                              28   82%                                                                              4,8,12-trimethyl-trideca-3,7,11-          1,6,10-trien-3-ol                                                                          500    15**            trienoic acid                             (nerolidol)                       2%                                                                              tert.-butyl 4,8,12-trimethyl-tride                                            ca-                                       1,000                               3,7,11-trienoate                                                           84%                                                                              isomer mixture                        54  3,7,11,15-Tetramethyl-                                                                     tert.-ButOH                                                                          2.5  300                                                                               8   72%                                                                              4,8,12,16-tetramethyl-heptadec-3-         hexadec-1-en-3-ol                                                                          500    7.5             enoic acid                                (isophytol)                       7%                                                                              tert.-butyl 4,8,12,16-tetramethyl-        490                                 heptadec-3-enoate,                                                         79%                                                                              isomer mixture                        55  Oct-1-en-3-ol                                                                              --     2.5  280                                                                              15   84%                                                                              non-3-enoic acid, bp.                                                         93-94° C./4 mbar                   1,210        --     7.5             q = 85:15                             56  3,7-Dimethyl-octa-1,6-                                                                     --     2.5  280                                                                              16   83%                                                                              4,8-dimethyl-nona-3,7-dienoic                                                 acid,                                     dien-3-ol (linalool)                                                                              7.5             bp. 120-124° C./4 mbar             1,500                               q = 82:18                             57  3-Methyl-but-1-en-3-ol                                                                     --     2.5  240                                                                              16   83%                                                                              4-methyl-but-3-enoic acid,                1,500        --     7.5  ***        bp. 70-71° C./4 mbar           58  3,7,11-Trimethyl-dodeca-                                                                   --     2.5  240                                                                              22   70%                                                                              trimethyl-trideca-3,7,11-trienoic         1,6,10-trien-3-ol                                                                          --     7.5             acid, bp. 165-170° C./1                                                mbar                                      560                                                                       __________________________________________________________________________     *Individual yields not determined                                             **nHexyldiphenylphosphine                                                     ***Temperature 80° C.                                             

We claim:
 1. A process for the preparation of a 4-substitutedbut-3-ene-1-carboxylic acid or its esters of the formula I ##STR5##where R¹ is an organic radical, R² is hydrogen or an organic radical,and R¹ and R² may furthermore be bonded to one another to form a5-membered to 20-membered ring and should be inert under the reactionconditions described below, and R³ is hydrogen or lower alkyl, bycarbonylation of a derivative of allyl alcohol with the aid of apalladium halide, wherein an allyl alcohol II ##STR6## is carbonylatedwith carbon monoxide at 50°-150° C. and under 200-700 bar,(a) togetherwith an alcohol III

    R.sup.3' --OH                                              (III)

where R^(3') is lower alkyl, if a predominant amount of an ester I is tobe prepared,or (b) without a further reactant where an acid I is to beprepared, in the presence of an effective amount of complex of apalladium halide and a tertiary phosphine (IV).
 2. A process as claimedin claim 1, wherein the carbonylation with carbon monoxide is carriedout at a temperature of 90° to 110° C. and under a pressure of 300 to600 bar.
 3. A process as claimed in claim 1, wherein the molar ratio ofphosphine to palladium is from 3:1 to 10:1.
 4. A process as claimed inclaim 1, wherein the amount of palladium is from 0.1 to 5 g per mole ofthe allyl alcohol II.
 5. A process as claimed in claim 4, wherein themolar ratio of phosphine to palladium is from 3:1 to 10:1.
 6. A processas claimed in claim 1, wherein the molar ratio of the alcohol III to theallyl alcohol II is from 2:1 to 6:1.